JPH01145891A - Manufacture of circuit substrate with solder bump - Google Patents

Abstract

PURPOSE:To form a solder bump in a through hole of a circuit substrate in which a connecting electrode can be freely disposed in the flat face of the substrate by forming the bump using the through hole of the substrate. CONSTITUTION:A through hole 3 is opened at a position for forming the solder bump of a substrate material which becomes a one-side pattern circuit substrate, the whole substrate is plated with electroless copper 4, printed with a pattern, developed, and formed by etching with the pattern. In this case, in order to form the bump at the non-pattern side, the pattern of the copper 4 is so formed as to reduce the area of the opening of the hole 3. Then, electrolytic copper 5 is plated on the copper 4 thereby to form the electrolytic copper in a protrusion state 6. Then, the copper 5 is nickel-plated and gold-plated at 7, printed with a solder resist 8 from the non-pattern side, a through hole 10 is partly filled with the resist 8, cured, solder is adhered by dipping in the opening of the hole 10 containing the electrode protrusion, and the bump is formed in the opening of the through hole.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to electronic circuit mounting in which a chip-on-board or hybrid circuit board on which bare ICs or electronic components are mounted is mounted on a motherboard using a solder reflow method or the like. , concerning high-density surface mounting to realize lightness, thinness, and size.

[Summary of the invention]

In the manufacturing process of circuit boards, the present invention can be applied to electrode copper plating, an intermediate process in which through-holes are formed using holes that penetrate electrode patterns on circuit boards, without any changes to conventional processing techniques. Utilizing the electric field concentration effect at the extremely small pattern electrode that occurs in the process, a circular copper protrusion is formed on the pattern electrode area around the through-hole opening, and a barrier metal layer and gold plating are further applied to the surface of the copper protrusion using this copper protrusion as a core. This is a method of manufacturing a circuit board in which processing is performed to form solder bumps. In addition, solder bumps are required to have flowability and self-alignment properties during solder reflow, and it is necessary to secure the amount of solder to maintain this property, so it is also possible to fill solder resist from the opening in the through hole using a printing method. This is an important manufacturing method for forming solder bumps according to the present invention.

[Conventional technology]

Conventionally, there have been no examples of providing solder bumps on circuit boards, but a similar technology includes electrodes for leadless chip carrier packages.

[Problem that the invention seeks to solve]

To mount a leadless chip carrier (LCC) pancage on a circuit board such as a motherboard and make circuit connections, solder, etc. The connection is fixed using . Therefore, L.C.C.
As the number of electrodes increases in a package, the outer periphery of the side surface becomes longer, resulting in an increase in the planar size of the pancage. Conversely, in order to suppress the planar size, it is conceivable to shorten the electrode pinches disposed on the outer periphery of the side surfaces, but this poses the problem of short circuits due to solder prefixes, which cannot be easily solved. As described above, in order to obtain a large number of electrodes required for an LCC package, there is a problem in that the area of the LCC circuit board must be increased only in order to arrange the electrodes on the outer periphery of the side surface. In addition, the electrodes used to fix these connections are arranged on the outer periphery of the side surface,
There is a problem of short circuits caused by solder bridges, which cannot be easily resolved. As mentioned above, in order to obtain a large number of electrodes in a leadless chip carrier package,
There is a problem in that the area of the circuit board of the leadless chip carrier has to be increased only in order to arrange the electrodes on the outer periphery of the side surface.

In addition, due to the restriction of arranging the electrodes used to fix these connections on the outer periphery of the side surface of the circuit board of the leadless chip carrier, jumper wiring using through holes is often used in the circuit wiring layout, and jumper wiring is used for external wiring. etc., and the cost amplifier was unavoidable, which became a problem. This invention enables the connection electrodes to be placed on the circuit board by forming solder bumps using the through holes of the circuit board, without the restriction that the side connection electrodes of the LCC package must be placed on the outer periphery of the carrier, that is, the circuit board. The present invention relates to a method for manufacturing a circuit board in which solder bumps are formed in through holes in the circuit board, which allow solder bumps to be freely arranged within the plane of the circuit board.

[Means for solving problems]

A method of manufacturing a circuit board according to the present invention in which a solder bump is formed in a through-hole opening of a circuit board reinforces the copper inner wall of the through-hole by forming the electrode of the through-hole opening that forms the solder hump to be small in plan view. During the electrolytic copper plating process, an electric field is concentrated on the electrode in the opening, and the electrolytic copper can be formed to swell in that area. The copper protrusions above the through-hole openings are important as solder bumps, and after the copper protrusions are formed, nickel plating or gold plating is similarly processed, and solder resist is applied by printing from the side of the circuit board opposite to the copper protrusions. Then, a part of the solder resist flows into the through hole, and if it is cured, it becomes possible to collect solder as a bump on the opening of the through hole.Furthermore, after applying flux, the solder resist is By performing dipping, solder bumps can be formed at the through-hole openings.

[Effect]

According to the method of the present invention, external connection electrodes, which are a feature of leadless chip carriers, can be formed using through holes in the circuit board without arranging them on the outer periphery of the circuit board.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings. In the figure, 1 is the substrate material, 2 is the copper foil pattern, and 3 is the through hole. When electroless copper 4 or electrolytic copper 5 is plated,
A through hole 10 is formed. FIG. 1 is a cross-sectional view showing a structure in which electrode protrusions 6 are formed at the openings of through-holes 3 of a single-sided patterned board by electrolytic copper plating, and solder 9 to serve as bumps is formed by dipping to cover the electrode protrusions 6. . The process of manufacturing the through-hole solder bump shown in FIG. 1 will be explained with reference to the sectional view shown in FIG. 2.

Figure 2 (al) is a board material that will become a single-sided pattern circuit board, Figure 2 (b) is a board material with through holes 3 drilled at the positions where solder bumps will be formed, and Figure 2 (C) is a board material that will become a single-sided pattern circuit board. The entire board is plated with electrolytic copper 4, as shown in Figure 2T.
dl is a state in which a pattern is formed by pattern baking and etching after development, and in this case, in order to form solder bumps on the non-pattern side, S electrolytic copper 4 is used to reduce the area of the opening of the through hole 3. A pattern is formed. FIG. 2 tel is a cross-sectional view of electrolytic copper 5 plated over electroless copper 4, but because of electrolytic copper plating,
At the opening of the through-hole 3 whose area is reduced, the current density flowing inside the plating bath is concentrated, and electrolytic copper is formed in the shape of a protrusion 6 in that area as shown. If this electrode protrusion 6 is a solder bump, when it is joined to an opposing pattern electrode by solder reflow etc., even if the solder of the solder bump flows out to the opposing pattern electrode, this electrode protrusion 6 will have the surrounding circuit pattern and circuit wiring. It has an important function of providing a gap to prevent contact with the solder bump substrate. FIG. 2(f) shows a state in which nickel plating and gold plating 7 have been applied on the electrolytic copper 5. Figure 2 T
In order to keep the solder 9 of the bump from coming out of the through-hole 10 and to collect it in the through-hole opening electrode, the solder resist 8 is printed from the non-patterned side, and a part of the through-hole 10 is covered with the solder resist 8. It is filled with. After hardening the solder resist, attach solder to the through-hole including the electrode projection by dipping, process flux, and reflow.
A solder bump having a cross-sectional shape as shown in the figure can be formed at the through-hole opening. 3 to 5 are views of other embodiments, and in FIG. FIG. 3 (bl) shows an example in which a through hole is formed from above the solder resist 8b printed on the non-electrode side, and a solder bump is formed by the above-mentioned manufacturing method. The solder resists 8a and 8b shown in Fig. 3 can be used to form similar solder bumps at the through-hole openings even if epoxy resin or laminated resin film is used. This is an example of forming a through-hole solder bump, which shows that solder bumps can be freely formed on either the front or back of the circuit board by selecting which side pattern to print the solder resist 8 filling the through-hole 10 from. Fig. 5 shows a cross-sectional view of an example of a through-hole solder bump using a multilayer board. Fig. 6 shows a conventional example of a leadless chip carrier, in which the connecting electrodes are connected to a circuit board. It is arranged on the outer periphery of the

[Effects of the Invention] According to the manufacturing method of the present invention, by providing a through hole in a circuit board, solder bumps can be easily formed at the openings of the through holes, and solder bumps can be easily formed at the openings of the through holes, which can be used for connections that were conventionally limited to the outer periphery of the circuit board. The electrodes can be provided inside the circuit board, and the number of electrodes can be increased without increasing the area of the circuit board. In other words, the effect of increasing the number of pins in a leadless chip carrier can be achieved. Furthermore, if metal pins in a plastic pin grid array package are replaced with the through-hole solder bumps of the present invention, it is possible to significantly reduce costs, and there is a significant effect in terms of quality in that problems such as pin bending are solved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a through-hole solder bump on a single-sided pattern circuit board, Figure 2 (al to
) and (bl are cross-sectional views of through-hole solder bumps formed on the pattern electrode side, FIG. 4 is a cross-sectional view of a double-sided pattern circuit board, and FIG. 5 is a cross-sectional view of a multilayer circuit board of at least 3N or more. 6 is a perspective view of a conventional leadless chip carrier. ゛1...Substrate material 2...Copper foil pattern 3...Through hole 4...Electroless plated copper 5 ... Electroplated copper 6 ... Electrode protrusion 7 ... Nickel plating and gold plating 8 ... Solder resist 8a, 8b ... Solder resist or epoxy resin or laminated resin film 9 ... Solder 10...Through hole or above Applicant: Seiko Keiyo Kogyo Co., Ltd. Main address 171 installation method Example Nobo 1 side view Condolence 4 Figure 1i! X criminal 1rl's I!

Claims (1)

[Claims] In a circuit board having a pattern on at least one side, a step of forming a through hole on a circuit pattern, a step of forming an electrode protrusion at an opening on one side of the through hole so as to surround the through hole, and a step of forming an electrode projection on one side of the through hole; 1. A method for manufacturing a circuit board with solder bumps, comprising the steps of: filling a through-hole opening facing the solder resist with solder resist; and covering the electrode protrusion with solder.